1. Field of the Invention
The invention relates to a method for evaluating the state of a fuel-air mixture and/or the combustion in a combustion chamber of an internal combustion engine, with sample signals of flame light signals, especially the flame intensity, being stored in a database, and with flame light signals, especially the flame intensity, of the combustion in the combustion chamber being detected and compared with the stored sample signals, and with an evaluation of the state being output in the case of coincidence between the measured and stored signal patterns.
2. The Prior Art
Increasingly stricter limit values for particle emissions require measures for providing the highest possible mixture quality, especially in internal combustion engines with direct injection.
The formation of particles in the combustion of hydrocarbon fuels occurs by sooting.
The reduction in the formation of particles is achieved by precise fuel metering, complete fuel evaporation and by mixing with the combustion air, so that in the end a homogeneous stoichiometric mixture is combusted. These goals place high demands on the injection system and the air-mass control, on processes which have an influence on the mixture formation, and on the charge turbulence.
In the NEDC test (New European Driving Cycle), the particle emissions are evaluated by the measured particle mass and the particle count. The predominant contribution to the emissions is made by starting the engine, the first load peaks of the still operationally cold engine and the high-load operation in the final phase of the test sequence. Strict limit values in the NEDC test can be fulfilled by internal combustion engines only if the initial contributions during the start run and the warm-up run are subjected to precise checks by injection and charge movement. Similarly, the contributions in high-load operation require precise transient tuning and cylinder balancing.
Development measures which have an influence on the mixture formation are aimed at producing finely misted fuel sprays which distribute in the combustion chamber and evaporate by the compression heat. Contact with the cold combustion chamber walls should be prevented because a once formed film on the wall cannot evaporate sufficiently, especially in the cold engine.
Examinations have shown that especially in the cold operating state in a multi-cylinder internal combustion engine, the individual cylinders are involved differently in the particle emissions, so that cylinder-selective measures need to be taken. The analyses of the causes of particle origination are gaining increasing importance in the engine development sequence.
A method for evaluating the state of a fuel-air mixture and/or the combustion in a combustion chamber of an internal combustion engine is known from AT 503 276 A2. Sample signals of flame light signals which are stored in a database and which are assigned to defined mixture states are compared with the patterns of measured flame light signals. In the case of coincidence between the measured and the stored signal patterns, conclusions are drawn on the state of the mixture in the combustion chamber. A precise and simple monitoring of the mixture state and the combustion can be achieved thereby.
A measuring device for evaluating the state of a combustible mixture is further known from FR 2 816 056 A1, with the measuring device comprising a spectrometer, fiber optics and an evaluation device which compares the determined measurement results of the detected spectrum with data stored in a database. The fiber optics connected to the spectrometer is in optical connection with a combustion chamber. The state of the combustible mixture can be determined by comparing the measured data with the signals stored in the database.
JP 2005-226 893 A shows a similar method for combustion diagnostics, with the light emission intensity of a combustion being detected and compared with signals stored in a database. A statement can be made on the state of the air-fuel mixture on the basis of the comparison.
It is the object of the invention to enable a monitoring of the particle emissions with the lowest possible effort.